A gyroscope is a device used for measuring or maintaining orientation and angular velocity; the gyroscope utilizes the angular momentum of a heavy spinning disk, called a rotor, to sense angular motion of its base about one or two axes at right angles to the spin axis. The rotor is mounted and moves within gimbals within a frame and maintains its orientation regardless of any movement of the base.
At high speeds, the gyroscope exhibits extraordinary stability of balance and maintains the direction of the high speed rotation axis of its central rotor. The implication of the conservation of angular momentum is that the angular momentum of the rotor maintains not only its magnitude, but also its direction in space in the absence of external torque. The fact that it will stay upright as long as it is spinning fast enough demonstrates the property of gyroscopic inertia: the direction axis resists change. This means that a gyroscope mounted universally, in double gimbals, will maintain the same orientation in space however its support is turned, a property applied in many navigational devices.
The first known apparatus similar to a gyroscope (the “Whirling Speculum” or “Serson’s Speculum”) was invented by John Serson in 1743. It was used as a level, to locate the horizon in foggy or misty conditions. But, the first instrument used more like an actual gyroscope was made by Johann Bohnenberger of Germany, who first wrote about it in 1817. The classic type gyroscope finds application in gyro-compasses, but there are many more common examples of gyroscopic motion and stability. Spinning tops, the wheels of bicycles and motorcycles, the spin of the Earth in space, even the behavior of a boomerang are examples of gyroscopic motion.